I heard, somewhere, a looong time ago, that Ford had a patent on the heated windscreen, and licensed the tech to other manufacturers for a royalty fee. Perhaps that's why it's not an option on the Leon? Dunno if that's even true, mind.
My old Mazda 3 had a heated screen, would deffo have gone for one in the Leon had it been available.
Ateca has one.
As for misting up... stop breathing for a few mins after setting off